Protein kinases (PKs) are enzymes which catalyze the phosphorylation of specific serine, threonine or tyrosine residues in cellular proteins. These post-translational modifications of substrate proteins can act as molecular switches to regulate cell proliferation, activation and/or differentiation. Aberrant or excessive PK activity has been observed in many disease states including benign and malignant proliferative disorders. It is frequently possible to regulate cellular activity in vitro and in many cases to treat diseases in vivo, such as proliferative disorders, by employing PK inhibitors.
In view of the large number of protein kinase inhibitors and the multitude of proliferative and other PK-related diseases, there is an ever-existing need to provide novel classes of compounds that are useful as PK inhibitors and thus in the treatment of these Protein Tyrosine Kinase (PTK) related diseases. What is required are new classes of pharmaceutically advantageous PK inhibiting compounds.
The Philadelphia Chromosome is a hallmark for chronic myelogenous leukaemia (CML) and carries a hybrid gene that contains N-terminal exons of the bcr gene and the major C-terminal part (exons 2-11) of the c-abl gene. This gene encodes a 210 kD protein, p210 Bcr-Abl, the Abl sequence of which contains the Abl-tyrosine kinase domain which is tightly regulated in the wild type c-Abl, but constitutively activated in the Bcr-Abl fusion protein. This deregulated tyrosine kinase interacts with multiple cellular signalling pathways leading to transformation and deregulated proliferation of the cells (Lugo et al., Science 247, 1079 [1990]).
Mutant forms of the Bcr-Abl protein have also been identified. A detailed review of Bcr-Abl mutant forms has been published (Cowan-Jones et al, Mini Reviews in Medicinal Chemistry, 2004, 4 285-299).